Ultralong hydroxyapatite nanowire-based layered catalytic paper for highly efficient continuous flow reactions

Herein, we report a new kind of highly flexible hydroxyapatite nanowire (HAPNW)-based layered catalytic paper with a high thermal stability, excellent fire resistance, and high catalytic efficiency for continuous flow catalysis. A simple process has been developed for preparing and loading gold nanoparticles (AuNPs) on the fire-resistant HAPNW paper to obtain the HAPNW/AuNP layered catalytic paper. Oleic acid molecules adsorbed on the surface of HAPNWs can effectively reduce Au(III) ions to Au nanoparticles in situ in aqueous solution in the absence of an additional reducing reagent at room temperature. The size and weight percentage of AuNPs and surface hydrophilicity/hydrophobicity of the HAPNW/AuNP layered catalytic paper can be controlled. Benefiting from the nanoporous network and nanowire-based layered structure, the HAPNW/AuNP layered catalytic paper exhibits high catalytic activity for continuous flow reactions when the aqueous solution flows through the paper. Additionally, the HAPNW/AuNP layered catalytic paper can be easily recycled. Importantly, the HAPNW/AuNP layered catalytic paper shows excellent nonflammable properties and high catalytic stability after heat treatment. The HAPNW/AuNP layered catalytic paper has a high catalytic efficiency (100%), good recyclability, long-term stability, and high thermal stability in the continuous flow catalytic reduction of 4-nitrophenol. Furthermore, the catalytic degradation of organic dyes is also investigated. The HAPNW/AuNP layered catalytic paper is promising for applications in water treatment and high-temperature catalysis. In addition, the fire-resistant HAPNW-based paper can be used as an excellent support for various catalysts to prepare other kinds of catalytic paper for many applications.